The invention pertains generally to energetic materials and in particular to a material capable of propagating detonation along a small channel.
The requirements for a detonation-transfer composition are great since detonation-transfer compositions are used in a pattern of thin channels that constitutes the detonation sequence or logic. The composition must be capable of being injection molded into a small channel, e.g., 0.2 to 1.5 mm in diameter, that curves and can have turns of 90.degree. or more. It is critical that all channels are continuously filled, thereby requiring the composition to initially flow into all open spaces in the pattern and resist cracking during cure, storage, and use. In addition to these rigorous physical properties, the composition must have equally rigorous explosive properties. The critical diameter, which is the smallest diameter of material that permits propagation of detonation, can not exceed 1.5 mm. The detonation velocity cannot be less than about 6500 meters/sec. Of course, the material must be relatively insensitive. If the ordnance having a detonation logic is to be stored, it is of great importance to have a stable detonation-transfer material. Unfortunately, materials that have small critical diameters and high detonation velocities generally have a lower sensitivity and stability.
Presently, the only DoD-certified detonation-transfer energetic composition comprises about 80 weight percent of pentaerythritol tetranitrate and the remainder of vinyl-terminated polydimethyl siloxane crosslinked with hydrogen-terminated polymethyl siloxane. The composition requires a certain platinum catalyst that causes several problems. Mix reproducibility is poor because the catalyst can be poisoned and can be easily misused. The mixed uncured explosive has a shelf-life at ambient temperature of only 24 hours, thus necessitating cold storage at a temperature from -29.degree. to -51.degree. C. Even at those temperatures, the shelf life is only eight months. Further problems are experienced with the physical strength of the cured material. These problems are due, in part, to the catalyst or improper storage and to the physical properties of the cured material. The net result of these problems is a very restricted use of energetic logic devices, despite a great need for these devices.
A possible energetic composition for transferring detonation is the composition that comprises vinyl-terminated polybutadiene-acrylonitrile copolymer crosslinked with an unsaturated ester and styrene and a cyclopolymethylene-polynitramine energetic filler. Tests have shown that the critical diameter and the detonation velocity of this composition are unsatisfactory. Even if the loading of this energetic filler were increased above 80 weight percent, the composition would still have a critical diameter and detonation velocity that would be still unsatisfactory. A different energetic filler is needed, but as was stated previously, energetic fillers giving a higher detonation velocity and a smaller critical diameter are also more sensitive, less stable, and decompose more easily when radiated. Another problem associated with the above composition is the increased difficulty in processing the composition because of the polymer. The particular crosslinked copolymer does not process as easily as the siloxane binder of the existing detonation-transfer composition. Processing in this discussion includes both compounding the composition and injection-molding the composition into a detonation-transfer link, i.e., a very small channel.